It is known in the art that aromatic carboxylates, such as potassium benzoate, when heated under pressure form aromatic polycarboxylates, e.g., dipotassium terephthalate and benzene. This disproportionation reaction can be advantageously carried out in the presence of a high-boiling aromatic dispersant, e.g., terphenyl.
Various methods for separating the dispersant from the aromatic polycarboxylates are broadly disclosed in the art, e.g., benzene extraction, evaporation, sublimation. The separation of the dispersant and the solids can also be effected by extraction with water at high temperature and pressure. This water extraction step is vulnerable to problems which are oftentimes associated with the settling and phase separation of large amounts of aqueous solutions mixed with large amounts of organic solutions. Evaporation or sublimation, on the other hand, is a slow and costly method, both with respect to the apparatus and to the energy necessary.